EPR study of Mn2+ doped nanocrystalline PbF2

Abstract.

Nanocrystalline samples of PbF2 doped with 0.05, 0.1, 0.4 and 1 mol%
Mn2+, used as paramagnetic probe, were prepared by inert gas
condensation technique. All the samples were vacuum annealed at different
temperatures to get different grain sizes. The X-ray diffraction studies
showed the dominant content of β-PbF2 phase with a fractional
quantity of α-PbF2. Thermal stability and sublattice melting
were studied by TGA and DSC respectively. EPR measurements were made on all
these samples at 77 and 300 K. The EPR spectra of all samples were found to
contain well resolved sextet arising from the Mn2+ ions that occupied
the cubic sites of Pb2+ ion of PbF2 lattice. The lower
concentration of the Mn2+ ions (0.05 and 0.1 mol%) clearly monitored
the Pb2+ environment in the PbF2 lattice. The 0.4 mol% showed
the presence of only the cubic sites with a minor concentration of the
orthorhombic sites. The spectra corresponding to 1 mol% Mn2+ clearly
showed two different components. The isotropic nature of the 1 mol%
as-prepared sample implied that there was no cluster formation and hence
this EPR spectrum was taken as the single ion spectrum. The annealed samples
contain two spectral components; one is from the isolated single ions and
the other one from the Mn2+ clusters. The spectral component of Mn2+ clusters was obtained by subtracting the spectrum for the
as-prepared sample for the spectra of annealed samples. The extracted
cluster phase spectra and the pure spectrum from the as-prepared sample were
then combined to simulate the entire set of experimental spectra. The
simulated spectra were found to be in good agreement with the experimental
data. The g values obtained were in the range very close to the free
electron g factor as the electrons are in the S state (L=0).